Third motion system for filament winding machine



Feb. 6, 1968 Rw. ES BAUG 3,367,586

THIRD MOTION SYSTEM'FOR FILAMENT WINDING MACHINE Filed Nov. 26, 1965 INVENTORI. Robert W. Eshbaugh BY ATTORNEY.

AGENT.

United States Patent 3,367,586 THIRD MOTIUN SYSTEM FOR FILAMENT WINDING MACHHNE Robert W. Eshbaugh, Norristown, Pa., assignor to the United States of America as represented by the Secretary of the Navy Filed Nov. 26, 1965, Ser. No. 510,455 3 Claims. (Cl. 242--2) ABSTRACT OF THE DISCLOSURE A filament winding machine is provided having a third controlled motion in order to wind geodesic or isotensoid filament paths on compound curved surfaces. The third motion servo-system includes metallized function generator paper on a rotating drum in conjunction with a curve follower.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to filament winding machines and more particularly to an improvement that provides a third controlled motion for incorporation in a conventional two motion filament winding machine in order to wind geodesic or similar strand paths on a compound curved surface.

The term filament winding system as used by the reinforced plastics industry denotes the equipment used to fabricate articles of continuous yarn or roving and resin. Several types of winding systems are used in the industry, the most common being the lathe, polar wrap and tumble wrap types. Although these systems differ in the mechanism of placing a strand upon a mandrel, each performs the same basic operations. They wrap and tension resin impregnated filaments upon a mandrel in a predetermined pattern. The lathe type of winding system offers the advantage over the polar and tumble wrap types of permitting a greater range of wind angles. With this type, the mandrel is mounted and rotated horizontally between centers, and the strand is fed onto the mandrel from the feedeye of a carriage which traverses back and forth parallel to the mandrel axis. Tensioning and strand impregnation are accomplished by other elements of the system.

While the basic two motion lathe type of winding system has proved most useful in fabricating fiber reinforced plastic sleeves and casings having general applications it has not been entirely satisfactory for the reason that it can only wind a strand in a helical path on the mandrel. For this reason a number of third motion lathe type winding systems have been developed. In these systems there is provided in addition to the motion of the mandrel and the motion of the carriage an additional motion of the feedeye relative to the axis of rotation of the mandrel. This third motion provides the capability of winding geodesic or isotensoid strand paths on compound curved surfaces. These third motion winding systems thus provide the flexibility that was lacking in the basic two motion systems; however, the use of these systems is prohibitive in many applications because of the greatly increased cost and complexity of the systems.

It is therefore an object of this invention to provide an improvement in a two motion lathe type of filament winding system which permits a third controlled motion in a simple and inexpensive manner.

It is another object of the instant invention to provide a third motion system which provides the capability of winding geodesic or similar strand paths on compound curved surfaces which system may be added to the basic two motion lathe type of winding system without extensive modifications.

It is a further object of this invention to provide an improvement in a lathe type of filament winding system which permits greater flexibility in the shapes of fiber reinforced plastic articles that can be fabricated without substantially increasing the per unit cost of the articles produced thereby.

According to the present invention, the foregoing and other objects are attained by providing a novel servo system which insures that the radial displacement of the feedeye from the mandrel will be the same each and every time the feedeye passes a given point on the mandrel as it traverses the mandrel during a Winding operation; This is achieved through the use of a servo drive unit for propelling the feedeye along a path which is substantially perpendicular to the axis of rotation of the mandrel. The servo drive unit receives its signal from a function generator which is preprogrammed according to the desired strand path to be wound on the mandrel.

The specific nature of the invention as well as other objects, aspects, uses and advantages thereof will clearly appear from the following description and from the accompanying drawing in which: 7

FIG. 1 is a diagrammatic view illustrating the effect of the third motion in winding a filament on a mandrel;

FIG. 2 is a schematic block diagram of a basic two motion lathe type filament winding system modified to provide a third controlled motion according to the present invention; and

FIG. 3 is a detailed schematic block diagram illustrating the third motion system according to the invention.

Referring now to the drawing wherein like reference numerals designate identical or corresponding parts throughout the several views and more particularly to FIG. 1 wherein the effect of the third additional motion in a lathe type filament winding machine is shown. For the purposes of the present illustration, the mandrel 11 is assumed to be a cylinder. On a cylinder a geodesic path is a constant helix angle. A strand placed in this path over the surface of the cylinder has no tendency to move sideways or twist when tensioned. If as shown in FIG. 1, a strand previously positioned at a constant helix angle 6 has its end displaced radially by a distance dx, a component of force normal to the strand is created. If this normal force is suflicient to overcome the frictional resistance, a portion of the strand will move, an angle change will be created, and the strand path will be modified as shown in FIG. 1. The new helix angle resulting from a radial displacement dx of the end of this strand is 6 the tendency of a tensioned strand to assume a geodesic path also holds for compound curved surfaces such as domes. A strand path can thus be modified by changing the distance of the feedeye from the mandrel.

As shown in FIG. 2 the lathe type winding system comprises a mandrel 11 mounted between a tail stock 12 and a headstock 13 for rotation about an axis by spindles 14 and 15, respectively. Spindle 15 is journaled in headstock 13 and is connected by way of beveled gears 17, shaft 18, and beveled gears 19 to a main drive shaft 21. Drive shaft 21 is connected by way of flexible drive 22, such as for example a belt or a chain, to the output shaft 23 of variable speed transmission 24. The input shaft 25 of variable speed transmission 24 is connected through flexible drive 26 to a prime mover 27.

A carriage 28 is mounted on a base 29 adjacent the mandrel 11 for transverse movement parallel to the axis of rotation of the mandrel. Transverse motion of the carriage 28 is accomplished by a drive mechanism generally indicated by sprockets 31 and 32 and a flexible drive 33. This drive mechanism is connected through a gearing mechanism 34 to the prime mover 27. The gearing mechanism 34 may include a second variable speed transmission. By selectively adjusting variable speed transmission 24 and the variable speed transmission in gearing mechanism 34 a wide range of rates of motion of mandrel 11 and carriage 28 may be achieved. The carriage 28 carries a feedeye 35 through which a strand of filament passes as it is wound on to mandrel 11. The strand of filament 36 is supplied by a source of filament generally illustrated by spools 37 and 38. The several filaments which comprise strand 36 are drawn from spools 37 and 38 over supply pulleys 39 into carriage 28 through tensioning and resin impregnating systems (not shown) and thence to feedeye 35.

The filament winding system as thus far described is a conventional lathe winding system and permits the winding of helical paths on a cylindrical mandrel. By this invention the third motion is achieved by a controlled motion variation of the radial distance between the mandrel 11 and the feedeye 35. Feedeye 35 is carried at the extremities of rods 41 which extend from housing 42 mounted on the carriage 28. A servo drive system 43 is connected by way of a motion translation system within housing 42 to the rods 41 and imparts a substantially vertical reciprocating motion to the feedeye 35 in response to a control signal. A function generator 44, which may be of the curve follower type, generates an electrical signal which is proportional to the winding path desired. This signal is supplied to serve amplifier 45 which in turn provides the driving voltage for servo drive system 43. Function generator 44 is mechanically synchronized with the transverse motion of carriage 28 through gear mechanism 34.

The third motion system is shown in greater detail in FIG. 3. Function generator 44 is synchronized through mechanism 34 to drive sprocket 32 of the carriage drive mechanism. Function generator 44 produces a voltage proportional to the x coordinate of a line drawn on the metallized graph paper which is on drum 46. The extension of feedeye 35 at each point of the carriage cycle is plotted on graph paper. The width of the metallized graph paper represents the extension of the feedeye 35, and the circumference of the drum represents one carriage cycle. As the curve follower probe 47 follows the line on drum 46, it moves the wiper arm 48 of a potentiometer, the winding 49 of which is connected across a source of constant voltage 51. There is thus generated at wiper arm 48 a varying voltage signal Which is proportional to the desired extension of feedeye 35. Wiper arm 48 is connected through single throw, double pole switch 52 and summing junctions 53 and 54 to the input of servo amplifier 45. Servo amplifier 45 generates a power signal which drives servo motor 55. A tachometer 56 is mechanically coupled to the output shaft of motor and produces an electrical output signal which is coupled to the second input of summing junction 54. The output shaft of motor 55 also mechanically drives the wiper arm 57 of a potentiometer having its winding 58 connected across a source of constant voltage 59. The wiper 57 is electrically connected to the second input of summing junction 53. The output voltage generated by tachometer 56 is proportional to the speed of servo motor 55, while the voltage across wiper arm 57 is proportional to the extension of the feedeye 35. These two signals serve to provide, respectively, a damping signal and a position signal to the servo amplifier. Servo motor 55 additionally drives a rotational to translational motion conversion device 61. Conversion device 61 may be, for example, a worm gear and ball worm shaft mechanism or a rack and pinion gear system. The rods 41 which support feedeye 35 are connected to the conversion mechanism 61. The feedeye 35 is thus propelled in and out in a reciprocating motion by servo motor 55 in response to a reference signal generated by function generator 44.

The feedeye position plot for the function generator 44 is initially established as follows: A mandrel is mounted in the machine with one cycle of the proper Winding pattern drawn on it. Then a strand is connected from the feedeye 35 to the mandrel 11 at the start of the pattern. The switch 52 is thrown to connect wiper arm 62 of a potentiometer having its winding 63 connected across a source of constant voltage 64 to the input of servo amplifier 45. The winding machine is then operated in short spurts of approximately 2 centimeters movement of the carriage at a time. At each stopped position, the wiper 62 of the potentiometer is adjusted to move the feedeye 35 in or out to the point where it keeps the strand on the pattern of the mandrel 11. At each point the potentiometer reading and the position of the function generator drum 46 are recorded. After one carriage cycle is completed in this fashion, the total plot is then drawn up on the metallized function generator paper. This provides an accurate first trial run for the third motion system. In most cases this plot taken under static conditions will have to be modified slightly because of the velocity lag in the servo control system.

It will be apparent that the embodiment shown is only exemplary and that various modifications can be made in construction and arrangement within the scope of the invention as defined in the appended claims.

What is claimed is:

1. In a filament winding machine comprising a mandrel mounted for rotation, a carriage adjacent said mandrel and mounted for transverse movement parallel to the axis of said mandrel, motive power means mechanically connected to said mandrel and to said carriage for rotating said mandrel and for translating said carriage at selective rates, a source of filament to be wound on said mandrel, a feedeye mounted on said carriage through which a filament from said source passes as it is wound on said mandrel, the improvement comprising a third motion system which provides the capability of winding geodesic or isotensoid filament paths on compound curved surfaces, said system comprising:

reciprocating means fixedly mounted on said carriage and carrying said feedeye at one extremity for imparting a reciprocating motion substantially perpendicular to the longitudinal axis of said mandrel to said feedeye during a winding operation,

function generating means connected to said reciprocating means for controlling the vertical extension of said feedeye at each point of the carriage cycle, said function generating means comprising a drum mounted for rotation and driven through said synchronizing means and having a curve representing the desired vertical displacement of said feedeye plotted about its surface,

curve follower means positioned adjacent said drum and mounted for transverse movement parallel to the axis of said drum for following the axial displacement of said curve as said drum rotates, and

signal conversion means connected to said curve follower means for converting the transverse position of said curve follower means to an electrical signal, said reciprocating means being connected to said signal conversion means and responsive to the signal generated thereby, and

synchronizing means connecting said function generating means to said carriage for synchronizing said function generating means with the translational movement of said carriage.

2. The improvement in a filament winding machine as recited in claim 1 wherein said reciprocating means includes a servo system which comprises:

a position servo having a servo amplifier and a servo motor, said servo amplifier being responsive to said electrical signal for producing an electrical power signal to drive said servo motor, and

motion conversion means driven by said servo motor and having said feedeye mounted thereon for converting the motion of said servo motor to a substantially vertical reciprocating motion.

3. The improvement in a filament winding machine as recited in claim 1 further comprising:

a manually adjustable variable voltage source, and

switch means interposed between said signal conversion means and said reciprocating means for selectively connecting said reciprocating means to said signal conversion means or to said manually adjustable variable voltage source whereby said curve on said drum may be empirically derived by determining selective points thereon through the process of adjusting the vertical extension of said feedeye during one cycle of said carriage by manually adjusting said adjustable voltage source when said switch means connects said adjustable voltage source to said reciprocating means.

References Cited UNITED BILLY S. TAYLOR,

STATES PATENTS Ponemon 2427 XR Bryant et a1. 242158 McCauley.

Hardwick 2422 Gaubatz 2427 X Primary Examiner. 

